Joel wants to find the best model for a bivariate data set that he is working with. He used a calculator to create a linear model, a quadratic model, and an exponential model. The coefficient of determination for the linear model was 0.45. The coefficient of determination for the quadratic model was 0.38, and the coefficient of determination for the exponential model was 0.51. Which model should he use to represent the data set? Justify your response in at least 2 sentences.